var book = {
    _year: 2004,
    edition: 1
  };
  Object.defineProperty(book, "year", {
      get: function(){
        return this._year;
      },
      set: function(newValue){
        if (newValue > 2004) {
          this._year = newValue;
          this.edition += newValue - 2004;
        }
      },
      enumerable : true,
    configurable : true,
        writable :true
  });
  
book._year = 20
console.log(book._year);